Previously, many attempts have been made in engine modifications replacing the head with a retrofit that utilizes the existing camshaft driving pushrods, rocker arms and four valves which are arranged in the classic "V" form of the intake and exhaust valves. In the past, a heavy and costly relay rocket system has been employed for this purpose as the normal pushrod location is very close to the cylinders creating mechanical complexity or unwieldness. Another approach, equally unwieldly has been tried employing particularly long rocker arms, however, bending deflections render this design rather impractical. Both the German Audi V-8 and the Volkswagon Rabbit engines have a combustion chamber, exhaust and intake valve grouping and inclination angle, that is similar in configuration with the invention, however, they use direct acting overhead camshafts on each set of valves. This approach is simpler and efficient only when incorporated as an initial design, as engines already in service are not able to be modified by the simple replacement of a high performance head as in the present invention because the cost of two to four camshafts and their drive system must also be included.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents were considered related:
______________________________________ PAT. NO. INVENTOR ISSUED ______________________________________ 4,819,591 Valentine 11 April 1989 4,023,543 Ishikawa 17 May 1977 3,884,199 Irimajiri et al 20 May 1975 2,884,913 Heintz 5 May 1959 2,863,429 Bouteleux 9 December 1958 2,700,966 Hofer 1 February 1955 ______________________________________
Valentine teaches a plurality of poppet valves positioned by their stems which are not all parallel. A rocker is mounted such that a rocking axis is produced transverse to each stem axis and the tappet elements are not on the same plane through the rocker axis. Each valve has an intermediate lift travel and the rocker axis is in line with the point of engagement with the tappet having the end face of the valve stem perpendicular to the valve stem axis.
Ishikawa discloses an auxiliary valve preventing any communication to the cylinder until the auxiliary valve has been lifted beyond a predetermined point.
Irimajiri et al utilize a valve operating system having main and auxiliary rocket arms for operating valves, each having a common upper tappet, push rod and lower cam operated tappet connected by a ball and socket joint. A similar cam operated assembly is provided for the exhaust valve which also employs a rocker arm for actuation.
Heintz teaches an internal combustion engine with the spark plug positioned between the intake and exhaust valve.
Hofer uses one rocker arm pivoted on either side of the cylinder head with a pivoted lever linkage arranged across the cylinder head opposite the camshaft with two inlet and two outlet valves disclosed.
For background purposes and as indicative of the art to which the invention relates, reference may be made to the remaining cited patent.